Lubrication

SNL housings in the 30, 31 and 32 series with labyrinth or taconite seals are intended for grease lubrication. For oil lubrication, housings with oil seals (→ Housings for oil lubrication) or Split plummer block housings SONL series should be used.

The lubricant should be selected based on the operating conditions of the bearing. For additional information, refer to Lubricant selection.

Initial grease fill

If no other requirements exist, the free space in the bearing should be completely filled with grease and the free space in the housing should be filled to 20 to 40% of its volume. A 40% grease fill is required when bearings have to be relubricated from the side, while a 20% grease fill is used when bearings are relubricated via the outer ring.

The housing base has markings to show the height of a 40% grease fill (fig. 1). For highly contaminated environments and slow speeds, fill the housing to 70–80%. For best protection against contaminants, use the SKF Three-Barrier Solution. For additional information, contact the SKF application engineering service.

Quantites for 20 and 40% grease fills are listed in table 1. The values are valid for a typical lithium grease (about 0,95 g/cm3). They include the grease for the bearing, but not the grease to fill the seals. For sealed bearings, the values have to be adjusted.

In most applications, the initial grease fill will adequately lubricate the bearing until the grease is exchanged during the next planned maintenance interval.

Relubrication

SNL plummer block housings enable relubrication of the incorporated bearings and seals. There are three drilled and tapped holes for an AH 1/8-27 PTF grease fitting: two in the cap (one centred and one offset), and one in the base. Each hole is sealed at delivery with a threaded plug.

Dimples cast into the top of the housing cap indicate alternative positions where holes can be drilled and tapped to accommodate a grease fitting. The two dimples on the outer sides of the central ridge indicate the position for lubrication holes for the seals.

The hole in the centre of the cap or the hole in the base should be used to relubricate spherical roller bearings with a relubrication feature (a lubrication groove and holes in the outer ring) (fig. 2). When applying grease via the relubrication feature, the shaft should be rotating. Narrow bearings (dimension series 13 and 22) in the locating position can be axially displaced, so that the relubrication groove in the bearing does not line up with the relubrication hole in the housing cap. Make sure the bearing is sufficiently centred when relubricating.